Britain could enjoy the hottest day of the year so far today as temperatures soar towards 33C (91F) after an official heatwave began for the first time since June.

Although temperatures have risen this high before in September, it is unusual for the heat to last so long, with the Met Office predicting up to six days above 30C (86F) for some areas – and the peak likely on Saturday with 33C (91F) highs in London. 

The UK Health Security Agency has upgraded its heat health alert to amber across every region of England apart from the North East, where a yellow alert is in place.

The six-day alert, which began yesterday and will run until Sunday night, warns of higher death rates and ‘significant impacts’ on vulnerable people and the NHS.

These impacts are likely to be felt across the health service, with those aged above 65 or those with pre-existing respiratory or cardiovascular disease at greater risk. 

But Britons will flock to parks and beaches today to enjoy the warmth as the mercury could top the current 2023 high of 32.2C (90.0F), recorded both on June 10 and 25.

It comes as autumn begins in an unseasonably warm fashion after a disappointing summer that saw Britain endure its sixth wettest July since records began. 

The Met Office said areas in West Yorkshire, Cornwall, Devon and Wales hit heatwave criteria yesterday, with more regions expected to be added to that list today.

While the hottest UK temperature recorded yesterday was 30.7C (87.3F) in West Sussex, forecasters said a new record is likely still to come.

Some 13 weather stations have now marked this period as an official heatwave, which is at least three days in a row with daily maximum temperatures meeting or exceeding the heatwave temperature threshold – a figure which varies by region.

Barbara Borges picks the perfect place to enjoy sun in the sea at Bournemouth beach today

Beachgoers enjoy the scorching temperatures on Brighton beach in East Sussex today

A woman swims at Jesus Green Lido in Cambridge today as people enjoy the hot weather

Met Office meteorologist Amy Bokota said: ‘As you go through the next couple of days quite a few extra (weather stations) will be added on to that [list]. 

’32C is expected today, 33C perhaps on Thursday, which is expected to be the peak. It will then be 32C right the way until Sunday for some places in the South.’

Temperatures are also set to reach 27C in Northern Ireland and Scotland, the Met Office said.

The mercury could start to drop gradually at the weekend and there is a chance of thunderstorms breaking out from the North and West of the country, the Met Office added.

Before then, the forecaster is watching a number of September heat records.

If the hottest day of 2023 is achieved this week, it would be the first time since 2016 – and before that the 1950s – that the UK’s warmest day of the year has happened in September.

In addition, the highest temperature of the year has happened in September in just four years over the last century.

There is also a chance of tropical nights this week, which is when overnight temperatures remain above 20C (68F).

The record highest overnight minimum temperature for September is 21.7C (71.1F), which the Met Office said could be challenged tonight and tomorrow night.

This week could also see the highest number of September days and highest number of consecutive September days on record where temperatures reach 30C (86F) or more.

However, the record for the warmest September day on record is unlikely to be broken this week. That record has stood since 1906 when temperatures reached 35.6C (96.1F) in Bawtry, South Yorkshire.

Met Office meteorologist Tom Morgan said: ‘A lot of people will probably think of the summer just gone as being pretty non-exceptional, pretty disappointing if you had plans in the UK. 

‘This week, it looks likely that we’ll see the highest temperature of the year so far. Today will be the third day that some sites have seen three consecutive days of heatwave conditions.

‘By the end of today, officially, it will be a heatwave, it is certain that it will be by tomorrow.’

The forecaster said this week will be the first prolonged spell of hot weather the UK has seen since June following an unusually wet July.

Another day of soaring temperatures brings people to Bournemouth beach in Dorset today

Beachgoers take shelter from the sun on Gyllyngvase Beach in Falmouth, Cornwall, today

The UK is also now dealing with a Saharan dust cloud, leaving deposits on cars and windows

Mr Morgan added: ‘We may well be close to some record-breaking temperatures in the next few days. The daytime maximum temperatures are a little less likely to be broken but nonetheless it will be hot so we are watching a couple of records.

‘The most likely record that we could see broken is the highest overnight temperature for Wales. Currently the September highest overnight temperature for Wales stands as 20.5C.

‘The highest UK September temperature we’ve ever seen still stands at 35.6C.

‘So we are very unlikely to see temperatures quite that high but probably a 33C is on the cards either today or maybe also on Thursday, so we are not too far away from the UK record either.’

Met Office chief meteorologist Neil Armstrong said high pressure situated to the South East of the UK was bringing more settled conditions and temperatures well above average for the time of year.

He added: ‘An active tropical cyclone season in the North Atlantic has helped to amplify the pattern across the North Atlantic, pushing the jet stream well to the north of the UK, allowing some very warm air to be drawn north.

‘It’s a marked contrast to the much of meteorological summer, when the UK was on the northern side of the jet stream with cooler air and more unsettled weather.’

The Met Office confirmed it has not issued an extreme heat warning, which covers the UK and aligns with the wider national severe weather warning service.

People play a card game as they enjoy the weather at Sefton Park in Liverpool this afternoon

A woman shields her face from the sun on Brighton beach today as temperatures soar again

Sunseekers flock to Bournemouth beach in Dorset today as they enjoy the sunshine

People walk and cycle through Hyde Park in London this morning on a very hot and sunny day

People make the best of the hot weather as they visit Land’s End in Cornwall today

However, there was a warning issued to pet owners to ensure animals have access to fresh drinking water, good ventilation and shade from direct sunlight.

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Dr Justine Shotton, senior vice president or the British Veterinary Association, said: ‘We may be past the peak summer months but it’s important to remember that this September sun and heat is also dangerous for animals.

‘Pets can be extremely susceptible to heat-related illnesses such as heatstroke, and can also suffer sunburn, heart conditions and breathing difficulties, many of which can sadly be fatal. Make sure all pets have access to fresh drinking water, good ventilation and shade from direct sunlight at all times.’

Meanwhile tourism chiefs and MPs criticised the ‘nannying’ warnings from the UK Health Security Agency about the weather yesterday.

The heat health alert, used in situations that can potentially put the whole population at risk, advised people to ‘stay hydrated and keep cool’.

But Conservative MP Peter Bone dismissed the ‘nanny state’ tone, saying: ‘There will be a time when there is a need for a real alert because temperatures are very high. The danger is if you issue them all the time, people ignore them. They ought to be careful about issuing alerts.’

Fellow Tory Giles Watling, MP for Clacton-on-Sea in Essex, added: ‘Obviously for those vulnerable people in society we’ve got to say be careful but I for one welcome the Indian summer. To issue a general warning to the whole population is overplaying it.’

Pedestrians walk in the midday sun past the Palace of Westminster in London today

Commuters pack on to a hot Jubilee line Underground train in Central London this morning

People cycle and jog through London today as the heatwave continues in England

A commuter with a portable handheld fan on a Jubilee line train in hot conditions today

Swimmers enjoy The Sky Pool at Embassy Gardens in London’s Wandsworth in the heat today

Sir Jacob Rees-Mogg branded the warning ‘ridiculously overblown’, adding: ‘It isn’t for the state to tell you to put on suncream or drink water.’

READ MORE Tourism chiefs and MPs hit out at ‘nannying’ weather warnings issued by forecasters

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Malcolm Bell, spokesman and until recently chief executive of Visit Cornwall, pointed out ‘beautiful sea breezes’ would make conditions more bearable along the coast.

He said: ‘The danger is people do the opposite when confronted by the nanny state. Just give them the facts and let them decide.’

And VisitEngland chief Patricia Yates said everyone should take ‘sensible precautions’ but urged them to use the ‘wonderful opportunity to get out and explore the outstanding tourism our country offers’.

The Met Office defines a heatwave as three consecutive days of a particular region exceeding a given threshold, which varies around the UK.

For Scotland, Wales, Northern Ireland, Cornwall and northern England, the threshold is 25C; for Somerset, Hampshire and the Welsh Borders, 26C; the south coast, East Anglia and the East Midlands, 27C; and for London and the home counties the threshold is 28C.

As the climate continues warming because of rising greenhouse gases, these hot spells will become more frequent and severe, the Met Office said.

People take shelter from the sun under umbrellas at St James’s Park in London today

Beachgoers enjoy the sun on Gyllyngvase Beach in Falmouth, Cornwall, this afternoon

Swimmers enjoy The Sky Pool at Embassy Gardens in London’s Wandsworth in the heat today

A swimmer enjoys the clear water and clean sands of Gyllyngvase Beach in Falmouth today

A visitor to Kew Gardens in West London enjoys the sunshine at the Grass Garden today

By 2070, it says 30C for two days or more will become more likely, with southern parts of the UK projected to see this happen 16 times more frequently than today.

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US-based, non-profit Climate Central calculated that the UK’s heatwave has been made five times more likely by climate change.

Scientists are seeing heat records broken on a near-continuous scale, with the Earth having just experienced its hottest ever Northern Hemisphere summer, the World Meteorological Organisation announced today.

Not only was it the hottest August on record, but it was the almost the hottest month ever measured, second only to July.

The average global temperature last month was 1.5C higher than the pre-industrial average, though this does not mean the target of the Paris Agreement has been breached as that refers to a decades-long average.

Last month also saw the highest global sea temperatures ever recorded, at an average of 21C.

Dr Friederike Otto of Imperial College London, and co-lead of World Weather Attribution, said: ‘This week’s heat in the UK has been made hotter by climate change that is the result of human activities like burning coal and other fossil fuels.

‘This is now the case for every heatwave, everywhere in the world. Until net greenhouse gas emissions end, heatwaves in the UK and elsewhere will continue to become hotter and more dangerous.’